U.S. patent application number 14/276031 was filed with the patent office on 2015-11-19 for system and method for controlling a multi-fuel engine to reduce engine pumping losses.
This patent application is currently assigned to GM Global Technology Operations LLC. The applicant listed for this patent is GM Global Technology Operations LLC. Invention is credited to Tameem K. ASSAF, Louis A. AVALLONE.
Application Number | 20150330325 14/276031 |
Document ID | / |
Family ID | 54361795 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150330325 |
Kind Code |
A1 |
ASSAF; Tameem K. ; et
al. |
November 19, 2015 |
SYSTEM AND METHOD FOR CONTROLLING A MULTI-FUEL ENGINE TO REDUCE
ENGINE PUMPING LOSSES
Abstract
A fuel control module, based on an engine torque request, fuels
N cylinders of an engine using a first fuel system. N is an integer
greater than zero. A throttle control module, based on the engine
torque request and the fueling of the N cylinders using the first
fuel system, opens a throttle valve to a predetermined wide open
throttle (WOT) position. A cost module, when the engine torque
request is greater than a predetermined torque: determines a first
cost value for fueling at least one of the N cylinders of the
engine using a second fuel system; and determines a second cost
value for adjusting at least one operating parameter other than
fueling of the engine. An adjustment module, based on, the first
and second cost values, one of: initiates the fueling of the at
least one of the N cylinders using the second fuel system; and
adjusts of the at least one operating parameter other than fueling
of the engine.
Inventors: |
ASSAF; Tameem K.; (Milford,
MI) ; AVALLONE; Louis A.; (Milford, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM Global Technology Operations LLC |
Detroit |
MI |
US |
|
|
Assignee: |
GM Global Technology Operations
LLC
Detroit
MI
|
Family ID: |
54361795 |
Appl. No.: |
14/276031 |
Filed: |
May 13, 2014 |
Current U.S.
Class: |
701/104 |
Current CPC
Class: |
F02D 41/26 20130101;
F02D 13/08 20130101; F02D 41/0025 20130101; Y02T 10/12 20130101;
F02D 41/0225 20130101; F02D 13/0219 20130101; B60W 10/10 20130101;
Y02T 10/30 20130101; F02D 41/30 20130101; F02D 19/061 20130101;
Y02T 10/36 20130101; Y02T 10/18 20130101; F02D 2200/0404 20130101;
F02D 19/0647 20130101 |
International
Class: |
F02D 41/30 20060101
F02D041/30 |
Claims
1. A control system of a vehicle, comprising: a fuel control module
that, based on an engine torque request, fuels N cylinders of an
engine using a first fuel system, wherein N is an integer greater
than zero; a throttle control module that, based on the engine
torque request and the fueling of the N cylinders using the first
fuel system, opens a throttle valve to a predetermined wide open
throttle (WOT) position; a cost module that, when the engine torque
request is greater than a predetermined torque: determines a first
cost value for fueling at least one of the N cylinders of the
engine using a second fuel system; and determines a second cost
value for adjusting at least one operating parameter other than
fueling of the engine; and an adjustment module that, based on the
first and second cost values, one of: initiates the fueling of the
at least one of the N cylinders using the second fuel system; and
adjusts of the at least one operating parameter other than fueling
of the engine.
2. The control system of claim 1 wherein the adjustment module
adjusts the fueling of the at least one of the N cylinders using
the second fuel system when the first cost value is less than the
second cost value.
3. The control system of claim 2 wherein the adjustment module
commands the adjustment of the at least one operating parameter
other than fueling of the engine when the second cost value is less
than the first cost value.
4. The control system of claim 1 wherein: the cost module
determines the second cost value for downshifting a transmission
from a current transmission gear ratio; and the adjustment module
selectively commands the downshift of the transmission based on a
comparison of the first and second cost values.
5. The control system of claim 1 wherein the cost module:
determines a first set of possible operating parameters based on
current operating parameters and based on fueling at least one of
the N cylinders of the engine using the second fuel system;
determines the first cost value based on the first set of possible
operating parameters; determines a second set of possible operating
parameters based on the current operating parameters and based on
adjusting the at least one operating parameter other than fueling
of the engine; and determines the second cost value based on the
second set of possible operating parameters.
6. The control system of claim 5 further comprising a torque limit
module that determines the predetermined torque based on the
current operating parameters.
7. The control system of claim 1 further comprising: the first fuel
system, wherein the first fuel system injects a first type of fuel;
and the second fuel system, wherein the second fuel system injects
a second type of fuel that is different than the first type of
fuel.
8. The control system of claim 7 wherein: the first type of fuel is
compressed natural gas (CNG); and the second type of fuel is
gasoline.
9. The control system of claim 1 further comprising: the first fuel
system, wherein the first fuel system injects a first fuel at first
locations associated with the cylinders, respectively; the second
fuel system, wherein the second fuel system injects a second fuel
at second locations associated with the cylinders, respectively;
and wherein the first locations are different than the second
locations.
10. The control system of claim 1 further comprising: the first
fuel system, wherein the first fuel system injects a first fuel
into intake ports associated with the cylinders, respectively; and
the second fuel system, wherein the second fuel system injects a
second fuel directly into the cylinders, respectively.
11. A control method for a vehicle, comprising: based on an engine
torque request, fueling N cylinders of an engine using a first fuel
system, wherein N is an integer greater than zero; based on the
engine torque request and the fueling of the N cylinders using the
first fuel system, opening a throttle valve to a predetermined wide
open throttle (WOT) position; when the engine torque request is
greater than a predetermined torque: determining a first cost value
for fueling at least one of the N cylinders of the engine using a
second fuel system; and determining a second cost value for
adjusting at least one operating parameter other than fueling of
the engine; and based on the first and second cost values, one of:
initiating the fueling of the at least one of the N cylinders using
the second fuel system; and adjusting of the at least one operating
parameter other than fueling of the engine.
12. The control method of claim 11 further comprising adjusting the
fueling of the at least one of the N cylinders using the second
fuel system when the first cost value is less than the second cost
value.
13. The control method of claim 12 further comprising commanding
the adjustment of the at least one operating parameter other than
fueling of the engine when the second cost value is less than the
first cost value.
14. The control method of claim 11 further comprising: determining
the second cost value for downshifting a transmission from a
current transmission gear ratio; and selectively commanding the
downshift of the transmission based on a comparison of the first
and second cost values.
15. The control method of claim 11 further comprising: determining
a first set of possible operating parameters based on current
operating parameters and based on fueling at least one of the N
cylinders of the engine using the second fuel system; determining
the first cost value based on the first set of possible operating
parameters; determining a second set of possible operating
parameters based on the current operating parameters and based on
adjusting the at least one operating parameter other than fueling
of the engine; and determining the second cost value based on the
second set of possible operating parameters.
16. The control method of claim 15 further comprising determining
the predetermined torque based on the current operating
parameters.
17. The control method of claim 11 wherein: the first fuel system
injects a first type of fuel; and the second fuel system injects a
second type of fuel that is different than the first type of
fuel.
18. The control method of claim 17 wherein: the first type of fuel
is compressed natural gas (CNG); and the second type of fuel is
gasoline.
19. The control method of claim 11 wherein: the first fuel system
injects a first fuel at first locations associated with the
cylinders, respectively; the second fuel system injects a second
fuel at second locations associated with the cylinders,
respectively; and the first locations are different than the second
locations.
20. The control method of claim 11 wherein: the first fuel system
injects a first fuel into intake ports associated with the
cylinders, respectively; and the second fuel system injects a
second fuel directly into the cylinders, respectively.
Description
FIELD
[0001] The present disclosure relates to internal combustion
engines and more particularly to multi-fuel control systems and
methods.
BACKGROUND
[0002] The background description provided here is for the purpose
of generally presenting the context of the disclosure. Work of the
presently named inventors, to the extent it is described in this
background section, as well as aspects of the description that may
not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted as prior art against the
present disclosure.
[0003] Internal combustion engines combust an air and fuel mixture
within cylinders to drive pistons, which produces drive torque. Air
flow into the engine is regulated via a throttle. More
specifically, the throttle adjusts throttle area, which increases
or decreases air flow into the engine. As the throttle area
increases, the air flow into the engine increases. A fuel control
system adjusts the rate that fuel is injected to provide a desired
air/fuel mixture to the cylinders and/or to achieve a desired
torque output. Increasing the amount of air and fuel provided to
the cylinders increases the torque output of the engine.
[0004] In spark-ignition engines, spark initiates combustion of an
air/fuel mixture provided to the cylinders. In compression-ignition
engines, compression in the cylinders combusts the air/fuel mixture
provided to the cylinders. Spark timing and air flow may be the
primary mechanisms for adjusting the torque output of
spark-ignition engines, while fuel flow may be the primary
mechanism for adjusting the torque output of compression-ignition
engines.
SUMMARY
[0005] A fuel control module, based on an engine torque request,
fuels N cylinders of an engine using a first fuel system, wherein N
is an integer greater than zero. A throttle control module, based
on the engine torque request and the fueling of the N cylinders
using the first fuel system, opens a throttle valve to a
predetermined wide open throttle (WOT) position. A cost module,
when the engine torque request is greater than a predetermined
torque: determines a first cost value for fueling at least one of
the N cylinders of the engine using a second fuel system; and
determines a second cost value for adjusting at least one operating
parameter other than fueling of the engine. An adjustment module,
based on the first and second cost values, one of: initiates the
fueling of the at least one of the N cylinders using the second
fuel system; and adjusts of the at least one operating parameter
other than fueling of the engine.
[0006] In further features, the adjustment module adjusts the
fueling of the at least one of the N cylinders using the second
fuel system when the first cost value is less than the second cost
value.
[0007] In still further features, the adjustment module commands
the adjustment of the at least one operating parameter other than
fueling of the engine when the second cost value is less than the
first cost value.
[0008] In yet further features: the cost module determines the
second cost value for downshifting a transmission from a current
transmission gear ratio; and the adjustment module selectively
commands the downshift of the transmission based on a comparison of
the first and second cost values.
[0009] In further features, the cost module: determines a first set
of possible operating parameters based on current operating
parameters and based on fueling at least one of the N cylinders of
the engine using the second fuel system; determines the first cost
value based on the first set of possible operating parameters;
determines a second set of possible operating parameters based on
the current operating parameters and based on adjusting the at
least one operating parameter other than fueling of the engine; and
determines the second cost value based on the second set of
possible operating parameters.
[0010] In still further features, a torque limit module determines
the predetermined torque based on the current operating
parameters.
[0011] In yet further features: the first fuel system injects a
first type of fuel; and the second fuel system injects a second
type of fuel that is different than the first type of fuel.
[0012] In further features: the first type of fuel is compressed
natural gas (CNG); and the second type of fuel is gasoline.
[0013] In yet further features: the first fuel system injects a
first fuel at first locations associated with the cylinders,
respectively; the second fuel system injects a second fuel at
second locations associated with the cylinders, respectively; and
the first locations are different than the second locations.
[0014] In still further features: the first fuel system injects a
first fuel into intake ports associated with the cylinders,
respectively; and the second fuel system injects a second fuel
directly into the cylinders, respectively.
[0015] A control method for a vehicle includes: based on an engine
torque request, fueling N cylinders of an engine using a first fuel
system, wherein N is an integer greater than zero; based on the
engine torque request and the fueling of the N cylinders using the
first fuel system, opening a throttle valve to a predetermined wide
open throttle (WOT) position; when the engine torque request is
greater than a predetermined torque: determining a first cost value
for fueling at least one of the N cylinders of the engine using a
second fuel system; and determining a second cost value for
adjusting at least one operating parameter other than fueling of
the engine. The control method further includes, based on the first
and second cost values, one of: initiating the fueling of the at
least one of the N cylinders using the second fuel system; and
adjusting of the at least one operating parameter other than
fueling of the engine.
[0016] In further features, the control method further includes
adjusting the fueling of the at least one of the N cylinders using
the second fuel system when the first cost value is less than the
second cost value.
[0017] In yet further features, the control method further includes
commanding the adjustment of the at least one operating parameter
other than fueling of the engine when the second cost value is less
than the first cost value.
[0018] In still further features, the control method further
includes: determining the second cost value for downshifting a
transmission from a current transmission gear ratio; and
selectively commanding the downshift of the transmission based on a
comparison of the first and second cost values.
[0019] In further features, the control method further includes:
determining a first set of possible operating parameters based on
current operating parameters and based on fueling at least one of
the N cylinders of the engine using the second fuel system;
determining the first cost value based on the first set of possible
operating parameters; determining a second set of possible
operating parameters based on the current operating parameters and
based on adjusting the at least one operating parameter other than
fueling of the engine; and determining the second cost value based
on the second set of possible operating parameters.
[0020] In further features, the control method further includes
determining the predetermined torque based on the current operating
parameters.
[0021] In further features: the first fuel system injects a first
type of fuel; and the second fuel system injects a second type of
fuel that is different than the first type of fuel.
[0022] In still further features: the first type of fuel is
compressed natural gas (CNG); and the second type of fuel is
gasoline.
[0023] In yet further features: the first fuel system injects a
first fuel at first locations associated with the cylinders,
respectively; the second fuel system injects a second fuel at
second locations associated with the cylinders, respectively; and
the first locations are different than the second locations.
[0024] In yet further features: the first fuel system injects a
first fuel into intake ports associated with the cylinders,
respectively; and the second fuel system injects a second fuel
directly into the cylinders, respectively.
[0025] Further areas of applicability of the present disclosure
will become apparent from the detailed description, the claims and
the drawings. The detailed description and specific examples are
intended for purposes of illustration only and are not intended to
limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The present disclosure will become more fully understood
from the detailed description and the accompanying drawings,
wherein:
[0027] FIG. 1 is a functional block diagram of an example engine
system;
[0028] FIG. 2 is a functional block diagram of an example control
system;
[0029] FIG. 3 is a functional block diagram of an example bi-fuel
control module; and
[0030] FIG. 4 is a flowchart illustrating an example method of
controlling fueling.
[0031] In the drawings, reference numbers may be reused to identify
similar and/or identical elements.
DETAILED DESCRIPTION
[0032] An engine combusts air and fuel within cylinders to generate
torque. Some engines can be fueled using two fuel systems and can
therefore be called bi-fuel engines. Different fuel systems can be
used to inject different types of fuel. Additionally or
alternatively, different fuel systems can be used to inject fuel at
different locations. For example, one fuel system may inject
gasoline and another fuel system may inject compressed natural gas
(CNG). As another example, one fuel system may inject fuel directly
into cylinders of the engine and another fuel system may inject the
fuel into intake ports associated with the cylinders.
[0033] Different types of fuel and different fuel injection
locations require different airflow conditions. For example, more
airflow into an engine is needed to achieve a stoichiometric
mixture of air and CNG than the airflow needed to achieve a
stoichiometric mixture of air and gasoline. An engine control
module (ECM) may open a throttle valve to increase airflow into the
engine.
[0034] According to the present disclosure, the ECM opens the
throttle valve for fueling that requires more airflow than another
type of fueling. Opening the throttle valve decreases pumping
losses of the engine. For example, the ECM may open the throttle
valve to a predetermined wide open throttle (WOT) position to
minimize pumping losses of the engine. The engine can also produce
more torque by changing the fueling of one or more cylinders
without having to adjust the throttle valve.
[0035] When a requested amount of engine torque is greater than a
predetermined torque, the ECM determines a first cost of changing
fueling and a second cost of changing one or more other operating
parameters, such as downshifting a transmission to a different gear
ratio. When the first cost is less than the second cost, the ECM
may change fueling of one or more cylinders of the engine. For
example, the ECM may switch from supplying CNG to a cylinder to
supplying gasoline to a cylinder, or switch from using port fuel
injection to using direct fuel injection for a cylinder. When the
second cost is less than the first cost, the ECM may command a
downshift of the transmission.
[0036] Referring to FIG. 1, an engine system 100 includes an engine
102 that combusts an air/fuel mixture to produce drive torque for a
vehicle. The engine 102 produces drive torque based on a driver
input from a driver input module 104. The driver input may be based
on a position of an accelerator pedal. The driver input may also be
based on a cruise control system, which may be an adaptive cruise
control system that varies vehicle speed to maintain a
predetermined following distance.
[0037] Air is drawn into the engine 102 through an intake system
108. The intake system 108 includes an intake manifold 110 and a
throttle valve 112. The throttle valve 112 may include a butterfly
valve having a rotatable blade. An engine control module (ECM) 114
controls a throttle actuator module 116, which regulates opening of
the throttle valve 112 to control the amount of air drawn into the
intake manifold 110.
[0038] Air from the intake manifold 110 is drawn into cylinders of
the engine 102. While the engine 102 may include multiple
cylinders, for illustration purposes a single representative
cylinder 118 is shown. For example only, the engine 102 may include
2, 3, 4, 5, 6, 8, 10, and/or 12 cylinders.
[0039] The ECM 114 may start and stop the engine 102 based on an
input received from an ignition system 120. The ignition system 120
may include a key or a button. The ECM 114 may start the engine 102
when a driver turns the key from an off position to an on (or run)
position or when the driver presses the button. The ECM 114 may
stop the engine 102 when a driver turns the key from the on
position to the off position or when the driver presses the button
while the engine 102 is running. The ECM 114 may deactivate one or
more cylinders while the engine 102 is running, which may improve
fuel economy under certain engine operating conditions.
[0040] The engine 102 may operate using a four-stroke cycle. The
four strokes, described below, are named the intake stroke, the
compression stroke, the combustion stroke, and the exhaust stroke.
During each revolution of a crankshaft (not shown), two of the four
strokes occur within the cylinder 118. Therefore, two crankshaft
revolutions are necessary for the cylinder 118 to experience all
four of the strokes.
[0041] During the intake stroke, air from the intake manifold 110
is drawn into the cylinder 118 through an intake valve 122. The ECM
114 controls an injector actuator module 123, which controls
opening of a fuel injector 124 and a fuel injector 125. The fuel
injectors 124 and 125 may inject fuel into intake ports associated
with the cylinders, into mixing chambers associated with the
cylinders, directly into the cylinders, or a combination of the
above. The injector actuator module 123 may halt injection of fuel
to cylinders that are deactivated.
[0042] The injected fuel mixes with air and creates an air/fuel
mixture in the cylinder 118. During the compression stroke, a
piston (not shown) within the cylinder 118 compresses the air/fuel
mixture. The engine 102 may be a compression-ignition engine, in
which case compression in the cylinder 118 ignites the air/fuel
mixture. Alternatively, the engine 102 may be a spark-ignition
engine, in which case a spark actuator module 126 energizes a spark
plug 128 in the cylinder 118 based on a signal from the ECM 114,
which ignites the air/fuel mixture. The timing of the spark may be
specified relative to the time when the piston is at its topmost
position, referred to as top dead center (TDC).
[0043] The spark actuator module 126 may be controlled by a timing
signal specifying how far before or after TDC to generate the
spark. Because piston position is directly related to crankshaft
rotation, operation of the spark actuator module 126 may be
synchronized with crankshaft angle. In various implementations, the
spark actuator module 126 may halt provision of spark to
deactivated cylinders.
[0044] Generating the spark may be referred to as a firing event.
The spark actuator module 126 may have the ability to vary the
timing of the spark for each firing event. The spark actuator
module 126 may even be capable of varying the spark timing for a
next firing event when the spark timing signal is changed between a
last firing event and the next firing event.
[0045] During the combustion stroke, the combustion of the air/fuel
mixture drives the piston down, thereby driving the crankshaft. The
combustion stroke may be defined as the time between the piston
reaching TDC and the time at which the piston returns to bottom
dead center (BDC). During the exhaust stroke, the piston begins
moving up from BDC and expels the byproducts of combustion through
an exhaust valve 130. The byproducts of combustion are exhausted
from the vehicle via an exhaust system 134. The exhaust system 134
includes a catalytic converter 136 that reduces emissions.
[0046] The intake valve 122 may be controlled by an intake camshaft
140, while the exhaust valve 130 may be controlled by an exhaust
camshaft 142. In various implementations, multiple intake camshafts
(including the intake camshaft 140) may control multiple intake
valves (including the intake valve 122) for the cylinder 118 and/or
may control the intake valves (including the intake valve 122) of
multiple banks of cylinders (including the cylinder 118).
Similarly, multiple exhaust camshafts (including the exhaust
camshaft 142) may control multiple exhaust valves for the cylinder
118 and/or may control exhaust valves (including the exhaust valve
130) for multiple banks of cylinders (including the cylinder
118).
[0047] The time at which the intake valve 122 is opened may be
varied with respect to piston TDC by an intake cam phaser 148. The
time at which the exhaust valve 130 is opened may be varied with
respect to piston TDC by an exhaust cam phaser 150. A valve
actuator module 158 may control the intake cam phaser 148 and the
exhaust cam phaser 150 based on signals from the ECM 114. When
implemented, variable valve lift may also be controlled by the
valve actuator module 158.
[0048] The valve actuator module 158 may deactivate the cylinder
118 by disabling opening of the intake valve 122 and/or the exhaust
valve 130. The valve actuator module 158 may disable opening of the
intake valve 122 and the exhaust valve 130 by decoupling the intake
valve 122 and the exhaust valve 130 from the intake camshaft 140
and the exhaust camshaft 142, respectively. In various
implementations, the intake valve 122 and/or the exhaust valve 130
may be controlled by devices other than camshafts, such as
electrohydraulic and/or electromagnetic actuators.
[0049] The engine system 100 may include a first fuel system 160
and a second fuel system 162. The first fuel system 160 includes a
fuel tank 164, a fuel pump 166, a fuel line 168, a fuel rail 170,
the fuel injector 124, and other fuel injectors for injecting fuel
from the fuel tank 164. The fuel tank 164 may store fuel such as
gasoline. The fuel pump 166 delivers fuel from the fuel tank 164 to
the fuel rail 170 through the fuel line 168. The fuel rail 170
distributes fuel to the fuel injector 124 and the other fuel
injectors that inject fuel from the fuel tank 164.
[0050] The second fuel system 162 includes a fuel tank 172, a fuel
pump 174, a fuel line 176, a fuel rail 178, and the fuel injector
125. The fuel tank 172 may store a second fuel, such as compressed
natural gas (CNG). The fuel pump 174 delivers fuel from the fuel
tank 172 to the fuel rail 178 through the fuel line 176. The fuel
rail 178 distributes fuel to the fuel injector 125 and other fuel
injectors of fuel from the fuel tank 172. The ECM 114 controls a
pump actuator module 179, which regulates the output of the fuel
pump 166 and the fuel pump 174 to achieve a desired pressure in the
fuel line 168 and the fuel line 176, respectively.
[0051] While the example where the first fuel system 160 injects
gasoline and the second fuel system 162 injects CNG, the present
application is applicable to other types of fuels. For example, the
first fuel system 160 may inject another liquid fuel, such as
liquefied petroleum gas (LPG), and the second fuel system 162 may
inject another gaseous fuel, such as vaporized LPG, or hydrogen.
Also, while the example of the first and second fuel systems 160
and 162 injecting different types of fuel is shown and described,
the present application is also applicable to fuel systems where
the same fuel can injected at two different locations, such as
directly into the cylinders and/or into intake ports of the
cylinders.
[0052] The engine system 100 may measure the position of the
crankshaft using a crankshaft position (CKP) sensor 180. The
temperature of the engine coolant may be measured using an engine
coolant temperature (ECT) sensor 182. The ECT sensor 182 may be
located within the engine 102 or at other locations where the
coolant is circulated, such as a radiator (not shown).
[0053] The pressure within the intake manifold 110 may be measured
using a manifold absolute pressure (MAP) sensor 184. In various
implementations, engine vacuum, which is the difference between
ambient air pressure and the pressure within the intake manifold
110, may be measured. The mass flow rate of air flowing into the
intake manifold 110 may be measured using a mass air flow (MAF)
sensor 186. In various implementations, the MAF sensor 186 may be
located in a housing that also includes the throttle valve 112.
[0054] A position of the throttle valve 112 may be measured using
one or more throttle position sensors (TPS) 190. The ambient
temperature of air being drawn into the engine 102 may be measured
using an intake air temperature (IAT) sensor 192. The ECM 114 may
use signals from the sensors to make control decisions for the
engine system 100.
[0055] The ECM 114 may communicate with a transmission control
module 196, for example, to coordinate shifting gears in a
transmission (not shown). The ECM 114 may also communicate with one
or more control modules of a vehicle, such as a hybrid control
module, a chassis control module, and/or a body control module.
[0056] Referring now to FIG. 2, a functional block diagram of an
example implementation of the ECM 114 is presented. A torque
request module 204 may determine a torque request 208 based on one
or more driver inputs 212, such as an accelerator pedal position, a
brake pedal position, a cruise control input, and/or one or more
other suitable driver inputs. The torque request module 204 may
determine the torque request 208 additionally or alternatively
based on one or more other requests, such as other torque requests
generated by the ECM 114 and/or torque requests received from other
modules of the vehicle, such as the transmission control module
196, the hybrid control module, the chassis control module, etc.
One or more engine actuators may be controlled based on the torque
request 208 and/or one or more other vehicle operating
parameters.
[0057] For example, a throttle control module 216 determines a
target throttle opening 220 based on the torque request 208. The
throttle actuator module 116 controls opening of the throttle valve
112 based on the target throttle opening 220. A spark control
module 228 may determine a target spark timing 232 based on the
torque request 208. The spark actuator module 126 controls spark
based on the target spark timing 232.
[0058] A fuel control module 240 determines first and second target
fueling parameters 244 and 248 for the first and second fuel
systems 160 and 162, respectively, based on the torque request 208.
For example only, the first target fueling parameters 244 may
include a target amount and timing for injection of gasoline, and
the second target fueling parameters 248 may include a target
amount and timing for injection of CNG. Setting of the target
fueling parameters 244 and 248 is discussed further below. The
injector actuator module 123 controls the first and second fuel
injection systems 160 and 162 to control fuel injection based on
the first and second target fueling parameters 244 and 248,
respectively.
[0059] A cylinder control module 252 may determine a target number
of cylinders to activate and/or deactivate based on the torque
request 208. The cylinder control module 252 may also determine
target intake and/or exhaust valve phasing angles based on the
torque request 208. Targets for controlling the intake and exhaust
valves of the cylinders are collectively illustrated by 256. The
valve actuator module 158 controls activation/deactivation and
phasing of the intake and exhaust valves of the cylinders based on
the target number of cylinders and the target valve phasing angles.
Fueling is disabled to deactivated cylinders. One or more other
engine actuators may additionally be controlled based on the torque
request 208.
[0060] Different fuels have different densities. For example, CNG
is less dense than liquid gasoline. A fuel that is less dense will
displace more air in a port fuel injection system and would require
higher manifold pressures to produce the same amount of torque as
another fuel that is more dense. Opening the throttle valve 112,
including opening the throttle valve 112 to a wide open throttle
(WOT) position, increases air pressure within the cylinders and
decreases pumping losses of the engine 102.
[0061] The following equation illustrates the oxidation of methane.
Methane is the ideal content of CNG fuel.
CH.sub.4+2O.sub.2.fwdarw.CO.sub.2+2H.sub.20
[0062] The stoichiometric air/fuel (A/F) ratio is a mass ratio
determined as follows, for example, for methane: [0063] 1. The
atomic weights are: Carbon (C) 12.01, Hydrogen (H) 1.008, Oxygen
(O) 16 [0064] 2. Molecular weight of
Methane=(1*12.01)+(4*1.008)=16.042 [0065] 3. Molecular weight of
Oxygen=2*16=32 [0066] 4. The Oxygen to fuel mass
ratio=(2*32)/(1*16.042)=64/16.042=3.99
[0067] 5. Oxygen comprises 23.2% of the mass of air so,
3.99.times.100/23.2=17.2 kg air.
[0068] Therefore, the stoichiometric air/fuel ratio of methane is
17.2:1. The following equation illustrates oxidation of
gasoline.
C.sub.8H.sub.18+12.5O.sub.2.fwdarw.8CO.sub.2+9H.sub.20
[0069] Using a similar determination, the stoichiometric air/fuel
ratio of gasoline can be determined to be 14.7:1.
[0070] The volumetric efficiency of methane is less than the
volumetric efficiency of gasoline because of methane's lower
density, which leads to greater intake charge displacement in a
port fuel injection (PFI) system. Volumetric efficiency corresponds
to actual airflow into a cylinder relative to a maximum value. PFI
systems are less volumetrically efficient than direct injection
systems due to the presence of intake charge displacement in PFI
systems. Direct injection systems do not displace intake charge due
to the injection of fuel directly into the cylinders.
[0071] Given the density of gasoline, methane, and air, the volumes
(mass/density) of air and fuel for each fuel necessary to attain
the respective stoichiometric air/fuel ratio can be determined. For
CNG:
V.sub.AIR=17.2 kg/1.204 kg/m.sup.3=14.29 m.sup.3,
therefore
V.sub.CNG=1 kg/0.668 kg/m.sup.3=1.50 m.sup.3,
[0072] For gasoline:
V.sub.AIR=14.7 kg/1.204 kg/m.sup.3=2.21 m.sup.3,
therefore
V.sub.GAS=1 kg/4.816 kg/m.sup.3=0.21 m.sup.3.
V.sub.AIR is the volume of air necessary to achieve the
corresponding stoichiometric air/fuel ratio. V.sub.CNG is the
volume of CNG necessary to achieve the stoichiometric air/fuel
ratio for CNG. V.sub.GAS is the volume of gasoline necessary to
achieve the stoichiometric air/fuel ratio for gasoline.
[0073] To determine the amount of power loss due to intake charge
(air) displacement, the follow equation can be used:
Power Loss=Volume of Fuel/(Volume of air+Volume of Fuel)
[0074] The following calculations are provided for a PFI system. In
the case of a direct injection system, there are no power losses
due to intake air displacement because the fuel is being injected
directly into the cylinder. In view of the above, the power losses
of gasoline and CNG are:
PL.sub.GAS=0.21/(12.21+0.21)=1.6%
PL.sub.CNG=1.50/(14.29+1.50)=9.5%,
where PL.sub.GAS is the power loss of gasoline and PL.sub.CNG is
the power loss of CNG.
[0075] Therefore, a gasoline system has approximately an 8 percent
(%) volumetric efficiency benefit over a CNG system due to intake
charge displacement. Also, gasoline fueling has the added benefit
of intake charge cooling due to the vaporization of liquid
gasoline, which increases volumetric efficiency over a CNG system.
As a result, a CNG-fueled engine would need to operate at higher
manifold pressures to produce the same amount of torque as a
gasoline engine.
[0076] According to the present disclosure, a bi-fuel control
module 260 commands the fuel control module 240 to generate the
second target fueling parameters 248 to provide CNG to one or more
of the cylinders of the engine 102. The fuel control module 240 may
set the first target fueling parameters 244 to provide gasoline to
zero, one, or more other cylinders of the engine 102.
[0077] Based on the provision of CNG to one or more of the
cylinders, the bi-fuel control module 260 also commands the
throttle control module 216 to increase the target throttle opening
220 (relative to if one or more additional cylinders were provided
with gasoline). For example only, the bi-fuel control module 260
may command that the target throttle opening 220 be set to open the
throttle valve 112 to the WOT position. Given the opening of the
throttle valve 112 to the WOT position, the bi-fuel control module
260 may also command the fuel control module 240 to set the second
target fueling parameters 248 to provide CNG fuel to a greatest
possible number of cylinders and to set the first target fueling
parameters 244 to provide gasoline to a least possible number of
cylinders to achieve the torque request 208. Opening the throttle
valve 112 further decreases pumping losses of the engine 102.
[0078] When the torque request 208 is greater than or equal to a
predetermined torque limit for current operating parameters 264
(e.g., current transmission gear ratio, number of cylinders being
provided with CNG, etc.), the bi-fuel control module 260 determines
a first cost value for switching a CNG fueled cylinder to being
fueled with gasoline. The bi-fuel control module 260 also
determines a second cost value for changing one or more of the
current operating parameters 264. For example, the bi-fuel control
module 260 may determine the second cost value for downshifting the
transmission.
[0079] When the first cost value is less than the second cost
value, the bi-fuel control module 260 commands the fuel control
module 240 to increase the number of cylinders that are gasoline
fueled, for example, by one. The increased opening of the throttle
valve 112 allows the engine 102 to produce more torque by switching
fueling of one or more cylinders from CNG to gasoline given the
opening of the throttle valve 112. Intake and exhaust valve phasing
of the cylinders being provided with gasoline can be optimized for
the use of gasoline, while intake and exhaust valve phasing of the
cylinders provided with CNG can be optimized for the use of
CNG.
[0080] When the second cost value is less than the first cost
value, the bi-fuel control module 260 commands the change in one or
more of the operating parameters 264. For example, the bi-fuel
control module 260 may command the transmission control module 196
to downshift the transmission. The bi-fuel control module 260 may
also adjust one or more engine actuators based on the
downshift.
[0081] As described above, while the example of increasing the
number of cylinders that are fueled with gasoline is presented, the
present disclosure is more generally applicable to increasing the
number of cylinders that are fueled using a more volumetrically
efficient fuel system. In the case of the injection of two
different types of fuels, the number of cylinders that are provided
with a more volumetrically efficient fuel is increased. In the case
of injection of one type of fuel in different locations, the number
of cylinders using a more volumetrically efficient fueling system
(e.g., direct injection) is increased.
[0082] Referring now to FIG. 3, a functional block diagram of an
example implementation of the bi-fuel control module 260 is
presented. A torque limit module 304 determines an engine torque
limit 308 based on the current operating parameters 264. For
example, the current operating parameters 264 include the number of
cylinders being fueled with CNG, the number of cylinders being
fueled with gasoline, the current transmission gear ratio, and
other operating parameters of the vehicle (and parameters that are
not controllable, such as ambient temperature and ambient
pressure). The current operating parameters 264 may be measured
using sensors and/or commanded or target parameters. The torque
limit module 304 may determine the engine torque limit 308 using
one or more functions and/or mappings that relate the current
operating parameters 264 to the engine torque limit 308.
[0083] A triggering module 312 generates a trigger signal 316 based
on the torque request 208 and the engine torque limit 308. For
example, the triggering module 312 may set the trigger signal 316
to a first state when the torque request is less than the engine
torque limit 308. The triggering module 312 may set the trigger
signal 316 to a second state when the torque request 208 is greater
than or equal to the engine torque limit 308. In various
implementations, a predetermined torque that is less than the
engine torque limit 308 may be used in place of the engine torque
limit 308. For example, a predetermined torque that is a
predetermined percentage of the engine torque limit 308 may be
used, where the predetermined percentage is less than 100%.
[0084] When the trigger signal 316 is in the second state, a cost
module 320 determines a first cost value 324 for increasing the
number of gasoline fueled cylinders by a predetermined number of
cylinders. For example only, the predetermined number of cylinders
may be 1 cylinder or 2 cylinders. The cost module 320 also
determines a second cost value 328 for changing one or more other
ones of the current operating parameters 264, such as for
downshifting the transmission.
[0085] The cost module 320 may determine a first possible set of
operating conditions based on the current operating parameters 264
and increasing the number of gasoline fueled cylinders (of the
current operating parameters 264) by the predetermined number of
cylinders and decreasing the number of CNG fueled cylinders by the
predetermined number of cylinders. The cost module 320 may
determine the first cost value 324 based on the first set of
possible operating conditions, such as using one or more functions
and/or mappings that relate sets of possible operating conditions
to cost.
[0086] The cost module 320 may determine a second possible set of
operating conditions based on the current operating parameters 264
and changing the transmission gear ratio (of the current operating
parameters 264) if the transmission was downshifted. The cost
module 320 may determine the second cost value 328 based on the
second set of possible operating conditions, such as using the one
or more functions and/or mappings that relate sets of possible
operating conditions to cost.
[0087] An adjustment module 332 compares the first and second cost
values 324 and 328. When the first cost value 324 is less than or
equal to the second cost value 328, the adjustment module 332
commands the fuel control module 240 to increase the number of
cylinders that are gasoline fueled and decrease the number of
cylinders that are CNG fueled by the predetermined number of
cylinders as indicated by 336. In response to the command 336, the
fuel control module 240 increases the number of cylinders that are
gasoline fueled and decreases the number of cylinders that are CNG
fueled. This allows the engine 102 to minimize the usage of
gasoline for a desired torque output. The increased opening of the
throttle valve 112 minimizes pumping losses.
[0088] When the second cost value 328 is less than the first cost
value 324, the adjustment module 332 commands the transmission
control module 196 to downshift the transmission as indicated by
340. The transmission control module 196 downshifts the
transmission in response to the command 340.
[0089] Referring now to FIG. 4, a flowchart depicting an example
method of controlling fueling of the engine 102 is presented.
Control may begin with 404 where the torque limit module 304
determines the engine torque limit 308 based on the current
operating parameters 264. The torque limit module 304 may also
determine the predetermined torque based on the engine torque limit
308 at 404.
[0090] At 408, the triggering module 312 may determine whether the
torque request 208 is less than the engine torque limit 308 or the
predetermined torque. If 408 is true, control may end. If 408 is
false, control may continue with 412. At 412, the cost module 320
determines the first and second cost values 324 and 328. The cost
module 320 determines the first cost value 324 based on increasing
the number of cylinders that will be fueled using the first (more
volumetrically efficient) fuel system 160 and the other ones of the
current operating parameters 264. The cost module 320 determines
the second cost value 328 based on changing one or more of the
current operating parameters 264, such as by downshifting the
transmission. The cost module 320 determines the first and second
cost values 324 and 328 using one or more functions and/or mappings
that relate possible operating conditions to cost.
[0091] At 416, the adjustment module 332 determines whether the
first cost value 324 is less than the second cost value 328. If 416
is true, the adjustment module 332 commands the fuel control module
240 to increase the number of cylinders that are fueled using the
first fuel system 160 at 420. The fuel control module 420 then
increases the number of cylinders that are fueled using the first
fuel system 160 by the predetermined number of cylinders (e.g., 1)
at 420, and control may end. If 416 is false, the adjustment module
332 commands the one or more operating conditions be changed. For
example, the adjustment module 332 may command the transmission
control module 196 to downshift the transmission at 424. Control
may end after 424. While the example of FIG. 4 is shown as ending,
FIG. 4 may represent one control loop, and control loops may be
executed at a predetermined rate.
[0092] The foregoing description is merely illustrative in nature
and is in no way intended to limit the disclosure, its application,
or uses. The broad teachings of the disclosure can be implemented
in a variety of forms. Therefore, while this disclosure includes
particular examples, the true scope of the disclosure should not be
so limited since other modifications will become apparent upon a
study of the drawings, the specification, and the following claims.
As used herein, the phrase at least one of A, B, and C should be
construed to mean a logical (A or B or C), using a non-exclusive
logical OR. It should be understood that one or more steps within a
method may be executed in different order (or concurrently) without
altering the principles of the present disclosure.
[0093] In this application, including the definitions below, the
term module may be replaced with the term circuit. The term module
may refer to, be part of, or include an Application Specific
Integrated Circuit (ASIC); a digital, analog, or mixed
analog/digital discrete circuit; a digital, analog, or mixed
analog/digital integrated circuit; a combinational logic circuit; a
field programmable gate array (FPGA); a processor (shared,
dedicated, or group) that executes code; memory (shared, dedicated,
or group) that stores code executed by a processor; other suitable
hardware components that provide the described functionality; or a
combination of some or all of the above, such as in a
system-on-chip.
[0094] The term code, as used above, may include software,
firmware, and/or microcode, and may refer to programs, routines,
functions, classes, and/or objects. The term shared processor
encompasses a single processor that executes some or all code from
multiple modules. The term group processor encompasses a processor
that, in combination with additional processors, executes some or
all code from one or more modules. The term shared memory
encompasses a single memory that stores some or all code from
multiple modules. The term group memory encompasses a memory that,
in combination with additional memories, stores some or all code
from one or more modules. The term memory may be a subset of the
term computer-readable medium. The term computer-readable medium
does not encompass transitory electrical and electromagnetic
signals propagating through a medium, and may therefore be
considered tangible and non-transitory. Non-limiting examples of a
non-transitory tangible computer readable medium include
nonvolatile memory, volatile memory, magnetic storage, and optical
storage.
[0095] The apparatuses and methods described in this application
may be partially or fully implemented by one or more computer
programs executed by one or more processors. The computer programs
include processor-executable instructions that are stored on at
least one non-transitory tangible computer readable medium. The
computer programs may also include and/or rely on stored data.
* * * * *